WASHINGTON - Federal regulators on Thursday approved the nation’s first over-the-counter birth control pill in a landmark decision that will soon allow American women and girls to obtain contraceptive medication as easily as they buy aspirin and eyedrops.

The Food and Drug Administration cleared once-a-day Opill to be sold without a prescription, making it the first such medication to be moved out from behind the pharmacy counter. The manufacturer, Ireland-based Perrigo, won’t start shipping it until early next year, and there will be no age restrictions on sales.

Hormone-based pills have long been the most common form of birth control in the U.S., used by tens of millions of women since the 1960s. Until now, all of them required a prescription.

Medical societies and women’s health groups have pushed for wider access for decades, noting that an estimated 45% of the 6 million annual pregnancies in the U.S. are unintended. Teens and girls, women of color and those with low incomes report greater hurdles in getting prescriptions and picking them up.

The challenges can include paying for a doctor’s visit, getting time off from work and finding child care.